The Israelites were punished for breaking the Sabbath (Nehemiah 13:17-18; Jeremiah 17:27). They were promised blessings for keeping the Sabbath (verses 21-26). Doesn't this show the importance of the Sabbath?
It shows the importance of the Sabbath in the old covenant system. As a sign, and as part of the tablets of the covenant, it showed covenant allegiance. The Israelites broke all aspects of the covenant, and they were punished with the curses that were attached to the covenant (Leviticus 26, Deuteronomy 28).
Their disobedience regarding the Sabbath, as well as their disobedience in worship rituals, was a sign of their unbelief. The blessings were physical, and the curses were physical, characteristic of the old covenant but not of the new.
The Jews were punished again in A.D. 70, but Sabbath-breaking was not the reason. Their primary sin in the first century was the rejection of the Messiah, who was far more important than the Sabbath. They had rejected the new covenant. Jesus was the "test commandment" of the first century. Faith in Christ is now the requirement on which our salvation and eternity depends.
In brief, God punished the Israelites for Sabbath-breaking because the Sabbath was a requirement for the time they lived in, for the covenant they lived under. But that cannot prove that the physical details of the Sabbath are still required in a different age.
The Sabbath was a blessing for both Jews and gentiles (Isaiah 56:2-8). Doesn't that show that both Jews and gentiles should keep it today?
Isaiah predicted that God, through the Suffering Servant, the Messiah, would establish a new covenant with his people (42:6-7; 49:8-10; 54:9-10; 55:1-3). However, in describing this new relationship, Isaiah also described old covenant customs that in some cases apply only figuratively to the new covenant. In Isaiah 56:7, for example, he said that gentiles will offer burnt offerings and sacrifices at God's house.
Isaiah's main point is that God not only cares for Israelites, but also for gentiles. God's house will become a place for all nationalities, and he will gather gentiles as well as Israelites (verse 8). Eunuchs, who were excluded from the temple in the old covenant (Deuteronomy 23:1), would also be accepted. The terms of relationship between God and humans would be changed, and a new covenant would be made.
God's house would "be called a house of prayer for all nations." Jesus quoted this scripture in Mark 11:17, but the real fulfillment of the prophecy is not in the physical temple, but in flesh in which the Spirit lives. Both Jews and gentiles are invited into God's household, the church. The physical details of Isaiah's prophecy — physical offerings and a physical temple — are not required for Christians today. If we interpret these physical details according to spiritual counterparts, perhaps we may interpret Sabbath-keeping in a spiritual way, too.
Is the Sabbath a physical detail, like offerings, or is it a permanent and intrinsic part of a proper relationship with God? Neither view should be assumed, and this passage does not give us enough information to decide. We must turn to the new covenant to understand how the Sabbath applies to Christians.
The Sabbath is a delight and honorable (Isaiah 58:13). Wouldn't it be wrong to call it burdensome and give up its benefits?
Isaiah 58 is a call to repentance. Isaiah is declaring to the house of Jacob their sins and rebellion (verse 1). Although the Israelites had an external appearance of worship (e.g., fasting), they did it for selfish reasons (verses 2-5). Although they claimed to worship God, they did not obey his more important ethical laws: justice, liberty and charity (verses 6-7).13
If the Israelites did the weightier matters of the law, then God would be responsive to them (verses 8-11). He would give physical blessings to the nation (verses 11-12) — and the same is true of the Sabbath. If the people were obedient to the covenant they were under, if they kept it without complaint, if they used God's day the way God wanted them to, then God would bless them physically.
Isaiah 58 is appropriate to old covenant conditions, and it does not necessarily tell us anything about new covenant requirements. We cannot assume that the requirements are the same. The old covenant laws were good, but their value was temporary. They were designed to lead us to Christ, and they applied until he came. The laws had benefits, but it is permissible for us to give them up after we are led to something better, and we cannot teach as requirement something that is actually optional.
Peter was inspired to say that the law of Moses was "a yoke that neither we nor our fathers have been able to bear" (Acts 15:10). Peter did not specify which aspects of the law were the most burdensome, but it is clear that the old covenant package was stricter, in external regulations, than the new covenant is. We must look to the new covenant to see whether 1) it tells us to look to the old covenant for worship days or 2) whether it gives new instructions regarding worship days and customs.
Prophecies describe a worship of God that includes the Sabbath (Isaiah 66:23; Ezekiel 44:24). Does this show that the Sabbath is a permanent aspect of God's law?
The prophets described an ideal time in which all peoples worshipped God. To effectively convey this concept to an old covenant nation, the prophets described old covenant forms of worship, including new moon observances (Isaiah 66:23; Ezekiel 46:3) and sacrifices in the temple (Zechariah 14:20-21; Ezekiel 20:40; 45:17; 46:4). They also describe discrimination against uncircumcised peoples (Ezekiel 44:9; Isaiah 52:1-2) and avoidance of ritual uncleanness (Ezekiel 44:25-27). But neither circumcision nor sacrifices are religious requirements in this age. Moreover, another prophecy indicates that the day-night cycle will cease (Revelation 21:25), implying that there will be no more Sabbaths.
Prophecies (whether New Testament or Old Testament, whether about Sabbaths or sacrifices or circumcision) are not a reliable source of proof regarding Christian practice. Our doctrines must be based on scriptures that are applicable to the age we live in.
13 The people complained about new moons in the same way that they complained about Sabbath restrictions (Amos 8:5). Although the Pentateuch does not forbid commerce on new moons, apparently that is the way they were observed in Amos's day. The people kept the days, but reluctantly. God criticized them most for social injustice. Hosea 2:11 similarly includes new moons among the "appointed feasts" being kept in Israel. Because injustice permeated the nation, God threatened to stop all the hypocritical worship.